摘要
Multiple morphologies of colloidal perovskite nanocrystals(NCs)diversify their optical and electronic properties.Among them,the linear absorption cross-section(σ)is a primary parameter to determine their intrinsic photophysical features,and consequently,application potential.Herein,three morphologies of all-inorganic hybrid colloidal perovskite CsPbBr_(3)NCs,nanocubes(NBs),nanoplatelets(NLs),and nanowires(NWs),were targeted,and their linearσvalues were obtained through femtosecond transient absorption(TA)spectroscopy analysis.At high excitation energy well above the bandgap,theσper particle of all CsPbBr3 NCs linearly increased with the particle volume(VNC)regardless of the morphology with the value ofσ400=9.45×10^(4)cm^(−1)×VNC(cm^(2)).Density functional theory(DFT)calculation confirmed the negligible influence of shapes on the optical selection rules.The Einstein spontaneous emission coefficients calculated from theσvalues define the intrinsic radiative recombination rate.However,reduced size dependence is observed when the excitation energy is close to the bandgap(i.e.,at 460 nm)with the value ofσ460=2.82×10^(8)cm0.65×(VNC)0.45(cm^(2)).This should be ascribed to the discrete energy levels as well as lower density of states close to the band edge for perovskite NCs.These results provide in-depth insight into the optical characteristics for perovskite NCs.
胶体钙钛矿纳米晶的形貌变化赋予其不同的光学和电子特性,其中,线性吸收截面是决定材料本征光物理特性及其应用潜力的主要参数.本文研究了三种不同形貌的全无机钙钛矿CsPbBr3纳米晶(纳米立方体、纳米片和纳米线),通过飞秒瞬态吸收光谱分析了它们的线性吸收截面值σ.在高于带隙的能量激发下,单个CsPbBr_(3)纳米晶的吸收截面值与形貌无关,且随着粒子的体积(VNC)呈σ400=9.45×10^(4)cm^(−1)×VNC(cm^(2))趋势变化.密度泛函理论证实了形貌对光学选择规则基本没有影响,同时,根据吸收截面值也计算得到了定义本征辐射复合率的爱因斯坦自发辐射系数.然而,当激发能接近带隙(460 nm)时,吸收截面值对纳米晶尺寸的依赖关系变弱,取值满足σ460=2.82×10^(8)cm0.65×(VNC)0.45(cm^(2)),这主要归因于钙钛矿纳米晶的离散能级及靠近带边的较低的态密度.本文的研究结果为洞悉钙钛矿纳米晶的光学特性提供了深入的见解.
作者
Fengying Zhang
Yuchen Liu
Shiqian Wei
Junsheng Chen
Ying Zhou
Rongxing He
Tonu Pullerits
Kaibo Zheng
张凤英;刘禹辰;卫诗倩;陈俊生;周莹;何荣幸;Tonu Pullerits;郑凯波(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation and School of New Energy and Materials,Southwest Petroleum University,Chengdu 610500,China;Department of Chemical Physics and NanoLund Chemical Center,Lund University P.O.Box 124,22100 Lund,Sweden;College of Chemistry and Chemical Engineering,Southwest University,Chongqing 400715,China;Department of Chemistry,Technical University of Denmark,DK-2800 Kongens Lyngby,Denmark)
基金
supported by the National Natural Science Foundation of China (NSFC, U1862111)
China Scholarship Council (201706990062)
Independent Research Fund Denmark-Nature Sciences (DFF-7014-00302)
Independent Research Fund Denmark-Sapere Aude starting grant (7026-00037A)
Swedish Research Council VR starting grant (2017-05337), grants VR2018-06011, and VR201805090
the Research Fund for international Young Scientists from NSFC, China (21950410515)
Swedish Energy Agency
